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1 Answer
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Quién is a interrogative/exclamative pronoun, so it must resplace a noun.

On the other hand qué can be an interrogative/exclamative pronoun (when referring to things) or and interrogative/exclamative adjective (when referring to people or things). So as we are talking about people it can only be an adjective so it has to go with a name.

You can find a complete explanation from RAE about the use of quién here and about the use of qué here.